VOLTAGE MONITORING CONTROLLING AND PROTECTING APPARATUS EMPLOYING PROGRAMMABLE UNIJUNCTION TRANSISTOR

• US 3,863,128 A
• Filed: 07/30/1973
• Issued: 01/28/1975
• Est. Priority Date: 07/30/1973
• Status: Expired due to Term

• Current Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Original Assignee: Dennis J. Wilwerding
• Inventors: Wilwerding, Dennis J.
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/384,066
• Time in Patent Office: 547 Days
• Field of Search: 307/252F,301 315/241P 320/21 321/2,14 323/20,22T,22SC
• US Class Current: 315/241.00P
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/3385 with automatic control of output voltage or current H02M3/33561 takes precedence
• CPC Class Codes: H05B 41/32 for single flash operation

Abstract

A PUT circuit compares a zener reference voltage with the voltage of an electronic flash storage capacitor, and starts and stops a battery powered d.c. to d.c. converter oscillator, which charges the capacitor, as necessary to maintain the capacitor voltage within desired limits. A zener diode in the PUT cathode circuit provides the desired hysteresis. A second PUT circuit compares a second zener reference voltage with the battery voltage, and stops the oscillator when the battery voltage drops to a predetermined minimum value.

Claims

1. Monitoring apparatus for effectively terminating the operation of a d-c to d-c converter oscillator when the output voltage thereof increases to a predetermined maximum value therefor, and for restarting the operation of the oscillator when the output voltage thereof decreases to a predetermined minimum value therefor, comprising a pair of conductors arranged for connection to the output of a d-c to d-c converter oscillator to cause an output voltage of said oscillator to appear between said conductors when said oscillator is operating, a programmable unijunction transistor having anode, cathode, and gate electrodes, reference voltage means connected between said gate and said cathode to establish therebetween a reference voltage of a predetermined value, means connecting said anode and said cathode between said conductors to cause said transistor to turn on and to conduct anode-cathode current when the value of the voltage between said conductors increases to a predetermined maximum value established by the value of said reference voltage, current responsive means connected to said transistor and to said oscillator and responsive to said anode-cathode current to effectively terminate the operation of said oscillator upon the appearance of said anode-cathode current, and a zener diode connected in series with said cathode to turn off said transistor, to effectively restart the operation of said oscillator, when the value of said voltage between said conductors decreases to a predetermined minimum value established by the zener rating of said diode.

2. Apparatus for terminating the charging of a capacitor when the voltage thereof reaches a predetermined maximum value therefor, and for restarting the charging of the capacitor when the voltage thereof decreases to a predetermined minimum value therefor, comprising a programmable unijunction transistor having anode, cathode, and gate electrodes, reference voltage means connected between said gate and said cathode to establish therebetween a reference voltage of a predetermined value, a capacitor connected to a source of charging current which, when operating, passes a charging current through said capacitor which progressively increases the voltage across said capacitor, means connecting said anode and said cathode across said capacitor, whereby said transistor turns on and conducts anode-cathode current when the value of the voltage across said capacitor increases to a predetermined maximum value established by the value of said reference voltage, current responsive means connected to said transistor and to said source of current and responsive to said anode-cathode current to terminate the operation of said source of current and the charging of said capacitor upon the appearance of said anode-cathode current, and a zener diode connected in series With said cathode to turn off said transistor, to restart the operation of said source of current, when the value of the voltage across said capacitor decreases to a predetermined minimum value established by the zener rating of said diode.

3. In electronic flash apparatus including a capacitor, a flash tube for selectively discharging said capacitor to produce flashes of light, and a d-c to d-c converter oscillator powered by a battery and connected to supply output voltage and charging current to said capacitor when said oscillator is operating, the improvement comprising a programmable unijunction transistor having anode, cathode, and gate electrodes, reference voltage means connected between said gate and said cathode to establish therebetween a reference voltage of a predetermined value, means connecting said anode and said cathode to said capacitor to produce between said anode and said cathode a voltage which is representative of the voltage across said capacitor, and to cause said transistor to turn on and to conduct anode-cathode current in an anode-cathode circuit when the voltage across said capacitor increases to a predetermined desired maximum value established by the value of said reference voltage, current responsive means connected to said anode-cathode circuit and to said oscillator and responsive to said anode-cathode current to effectively terminate the operation of said oscillator and the charging of said capacitor upon the appearance of said anode-cathode current, thereby to prevent the voltage across said capacitor from exceeding said maximum value, and a zener diode connected in series with said cathode in said anode-cathode circuit to turn off said transistor, to restart the operation of said oscillator, when the voltage across said capacitor decreases to a predetermined desired minimum value established by the zener rating of said diode.

4. Apparatus as specified in claim 3, wherein said reference voltage means includes a resistor and a zener diode connected in series across said capacitor, and includes means connecting the last mentioned diode between said gate and said cathode.

5. Apparatus as specified in claim 3, including a second programmable unijunction transistor having anode, cathode, and gate electrodes, second reference voltage means connected between said anode and said cathode of said second transistor to establish therebetween a second reference voltage of a predetermined value, means connecting said gate and said cathode of said second transistor to said battery to produce between said gate and said cathode of said second transistor a voltage which is representative of the voltage across said battery, and to cause said second transistor to turn on and to conduct anode-cathode current in an anode-cathode circuit when the voltage across said battery decreases to a predetermined minimum value established by the value of said second reference voltage, and means connecting said anode-cathode circuit of said second transistor to said current responsive means to cause the latter to effectively terminate the operation of said oscillator and the discharging of said battery upon the appearance of said anode-cathode current of said second transistor, thereby to prevent said oscillator from reducing the voltage across said battery below said minimum value.

6. Apparatus as specified in claim 5, wherein said battery is a rechargeable battery of the nickel-cadmium type.

7. Apparatus as specified in claim 5, wherein said current responsive means includes a cut-off transistor which is so connected to the said anode-cathode circuit of each of said unijunction transistors as to turn on upon the appearance of said anode-cathode current in either of said anode-cathode circuits, and wherein said cut-off transistor is so connected to said oscillator as to prevent the latter from oscillating when said cut-off transistor is turned on.

8. In electronic flash apparatus including a capacitor, a flash tube foR selectively discharging said capacitor to provide flashes of light, and a d-c to d-c converter oscillator powered by a battery and connected to supply output voltage and charging current to said capacitor when said oscillator is operating, the improvement comprising a programmable unijunction transistor having anode, cathode, and gate electrodes, reference voltage means connected between said anode and said cathode to establish therebetween a reference voltage of a predetermined value, means connecting said gate and said cathode to said battery to produce between said gate and said cathode a voltage which is representative of the voltage across said battery, and to cause said transistor to turn and latch on and to conduct anode-cathode current in an anode-cathode circuit when the voltage across said battery decreases to a predetermined minimum value established by the value of said reference voltage, and current responsive means connected to said anode-cathode circuit and to said oscillator and responsive to said anode-cathode current to effectively terminate the operation of said oscillator and the discharging of said battery upon the appearance of said anode-cathode current, thereby to prevent said oscillator from reducing the voltage across said battery below said minimum value, said transistor remaining latched on notwithstanding any rise in the voltage across said battery which occurs upon said termination of the operation of said oscillator.

9. Apparatus as specified in claim 8, wherein said reference voltage means includes a resistor and a zener diode connected in series across said battery, and includes means connected said diode between said anode and said cathode.

10. Apparatus as specified in claim 8, wherein said battery is a rechargeable battery of the nickel-cadmium type.

11. Apparatus as specified in claim 8, including a signalling means connected to respond to said anode-cathode current and producing a signal in the presence of said anode-cathode current.